5W-20 vs. 5W-30 Motor Oil

by Amy Rodriguez

The weight, or viscosity, of a motor oil determines the labeling it is sold under. Weights such as 5W-20 and 5W-30 are very close numerically, but have distinct viscosity differences


The numbering system of the motor oil industry normally gives two values within the label. For example, a 5W-20 rating signifies that its cold pour point is at 5 degrees Celsius. The W stands for the grade type, which is winter; and the 20 is the viscosity index expressed at 100 degrees Celsius.


The difference between 5W-20 and 5W-30 is that the lower viscosity in 5W-20 makes it a base stock oil that is very thin and geared toward winter use. In contrast, 5W-30 has more oil additives, as well as thicker base stock oil, making it a bit difficult to stay within its weight grade as a vehicle ages with mileage.

Expert Insight

Overall, both 5W-20 and 5W-30 weight oils are used during all seasons of the year, mainly for overhead cam engines.

About the Author

Writing professionally since 2010, Amy Rodriguez cultivates successful cacti, succulents, bulbs, carnivorous plants and orchids at home. With an electronics degree and more than 10 years of experience, she applies her love of gadgets to the gardening world as she continues her education through college classes and gardening activities.

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